The cochlear implant is the first neural prosthesis to achieve the technical success necessary for widespread clinical application. It provides the only effective therapy for restoring sound sensation to the profoundly deaf. Over the past 15 years dramatic advances in patients' performance with these devices have been achieved (e.g., adults' average sentence recognition scores of 70-80% without speechreading). These advances have derived substantially from the collective efforts of researchers in a broad array of scientific disciplines. This close collaboration and cooperation has been fostered in large part through a series of biennial research conferences, originating with the 1983 Gordon Research Conference on Implantable Auditory Prostheses. These conferences are the only forum in which implant research issues are the sole focus. The major goal of the 1997 conference is to continue this long standing tradition of providing a forum for the focused discussion and serous scientific exchange which is crucial to continued progress in the field. This conferences's theme is to understand factors underlying the wide variation of implantees' speech recognition scores, one of the 1995 NIH Consensus Conference's recommendations for future research. The first day's sessions will address factors affecting speech perception performance in adults and children as well as spoken language processing (including implantees' results on new, lexical-access based speech tests). During the next 3 + days, important new insights into sources of individual variability will be described from a number of perspectives (e.g., imaging of implanted electrode positions, temporal and spatial representations of electrically evoked whole nerve potentials from intracochlear measurements, neurophysiologic processes underlying speech sound perception and auditory cortical maturation, and narrowly focused versus diffuse electrical fields). With over 14, 000 existing implant patients and the number increasing rapidly, there is considerable urgency to understand basic issues of implant design and programming. This understanding will lead to an individualized approach to selection of stimulation parameter sets for present and future speech processing strategies; the goal is to optimize an implantee's speech recognition. Implants directly stimulate the auditory nerve, bypassing the normal processing that occurs in the cochlea, and thus provide a unique opportunity to study the relative roles of central and peripheral processing in auditory perception. This application seeks partial support for this conference.